Managing personal Outlook.com account settings, security, and privacy
1
On your account activity if you are seeing login attempts, that indicates some bot is trying to hack your account, are any of those login attempts indicated as successful or are they unsuccessful?
Also on your account online, check your profile details, do you only see your own Email address listed there, and no Email address you do not recognize?
2
In the meantime, you need to ensure you have a long and strong password set on your account and also enable 2 factor authentication on your account as an extra layer of security.